P13631: Gravity Fed Flow Process Control
Teaching Aid
Introduction
Cart Layout
Theory
Draining a tank is a non-integrating (or selfregulating) process. A constant liquid level
corresponds with an inlet flow set to match the
outlet flow via the control valves on the cart.
This is conveyed through equations below:
An RIT education couples theory in lecture
with practical application in lab. In the past,
carts have been built by senior design groups
to demonstrate lecture concepts. This project
combines the dynamics of a gravity drained
tank with LabVIEW to teach process control.
The team progressed from theoretical design
and planning to implementation over the
course of 7 months. The final result is a
functioning cart to teach process control.
Project details can be found at our website:
http://edge.rit.edu/edge/P13631/public/Home
Gc = controller transfer function
Kc = controller gain from tuning
KaKp = Kc; the actuator and process gains
Τc = controller time constant
Τv = valve time constant
S = transfer function variable in the Laplace
transform space
τI = integration time constant
Kp = process time constant
Customer Needs
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Safety and ergonomics
Student learning
Transportability
Ease of maintenance
Minimal water use
Minimal cost
Interface with LabVIEW
Combining all process dynamics yields:
Design Process
Cart Features
Y(s) = output of process
Ys(s) = set point of process
Gd = derivative transfer function
D(s) = disturbance output
Gc = controller transfer function
Ga = valve transfer function
Gp = process transfer function
Gs = level or flow transmitter transfer function.
• Leaf table to increase student
workspace
• Aluminum bracketing to
decrease weight and increase
mobility
• Wheels and brakes to increase
mobility and practicality
Testing Results
Safety Testing
Result
Functionality Testing
Center of gravity
Pass
Stress and
deflection
Pass
Process
constants
Gain
(inches/percent
open)
Time constant
(min)
Electricity
grounding
Pass
Control Valve 1
0.9
15.37
Control Valve 2
1.6
7.45
Conclusions and Recommendations
The final cart meets customer needs and can be used by students to
safely learn about process control. Improvements for the future include:
Reducing water use
• Install a pump to reroute water to supply instead of drain.
• Install an additional holding tank for water with a
recirculation pump.
The group chose the line pressure cart that used a sink
faucet to supply water at approximately 45 psi. Based
on the Pugh chart and risk analysis, that design had the
fewest number of risks.
Testing time to complete lab procedure
• Conduct a time trial with 4th year Chemical Engineering
students and the lab manual to confirm each day takes
three hours to complete.
Team Members (left to right):
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Lead Engineer: James Brinkerhoff, ChE
Project Manager: Christopher Kulbago, ChE
Fluids Specialist: Lauren Pahls, ChE
Team Facilitator: Sarah Salmon, ChE
Electrical Lead: Ted Rakiewicz, EE
Mechanical Lead: Patrick O’Connell, ME
This project was made possible by our faculty guide,
Steve Possanza, our customer, Dr. Richter, our process
controls professor, Dr. Sanchez, and the Chemical
Engineering Department Lab Technician, Paul Gregorius.